Background

This report provides a brief summary of the weekly ensemble forecast for Maine from the COVID-19 Forecast Hub. In collaboration with the US CDC, our team aggregates COVID-19 forecasts from dozens of teams around the globe. Typically on Wednesday of each week, a summary of the week’s forecasts from the COVID-19 Forecast Hub appear on the official CDC COVID-19 forecasting page.

Every week, teams submit their forecasts to the COVID-19 Forecast Hub.

Each Tuesday, we combine the most recent forecasts from each team into a single “ensemble” forecast of reported COVID-19 cases at the county, state, and national level and deaths at the state and national level. At the moment, we only generate ensemble forecasts for four weeks into the future, as the available evidence suggests that models are less accurate at longer forecast horizons.

Weekly reports from the COVID-19 Forecast Hub can be found at this page.

COVID-19 Mortality Forecasts

Since the inputs to the ensemble model do not factor in changes in behavior or policy that could have an impact on short-term disease transmission (e.g. school openings or closures, new interventions, governmental policy shift, etc…), the ensemble model itself should not be looked to for specific answers to questions like “what will happen if or when schools open in 2 weeks” because most of the input models are not factoring in these changes. That said, the ensemble model has consistently shown strong predictive performance, and very few of the many interventions put in place appear to have created dramatic changes in short-term disease transmission that would impact short-term trends in mortality.

State level

This week, our ensemble combined forecasts for Maine from 46 different models.

At the state level, the ensemble model predicts that weekly totals of observed deaths in each of the next four weeks will be between 13 and 14 deaths each week with around 800 total deaths by April 03 (Figure 1). However for the week ending April 03, the ensemble shows substantial uncertainty, with observed deaths between 0 and 40 deemed possible (95% prediction interval: 2 - 37).

During periods of relative stability, models in general show broad agreement about the predicted trajectory of the outbreak. However, when there are steep surges or declines in cases or deaths, models often have quite different predictions for the upcoming weeks. The result is that there is increased uncertainty in the ensemble forecast, which can be seen as wider confidence intervals in the forecast visualization. You can explore the full set of models, including their forecasts for past weeks online at our interactive forecast visualization.

Figure 1: Weekly observed and forecasted COVID-19 deaths. Observed data from JHU CSSE and forecasts from the COVID-19 Forecast Hub.

Figure 1: Weekly observed and forecasted COVID-19 deaths. Observed data from [JHU CSSE](https://github.com/CSSEGISandData/COVID-19/tree/master/csse_covid_19_data/) and forecasts from the [COVID-19 Forecast Hub](https://covid19forecasthub.org/).

For state-level death forecasts made over the last 6 weeks in Maine for which observed data are now available, the 95% prediction intervals covered the truth 44% of the time, and the 50% prediction intervals covered the truth 11% of the time.

The sortable and searchable table below shows the total number of reported COVID-19 deaths at the US level and for Maine over the last two weeks (February 21, 2021 to March 06, 2021) and the forecasted counts for the subsequent two weeks (March 07, 2021 to March 20, 2021).

COVID-19 Incident Case Forecasts

State level

At the state level, the ensemble model predicts that weekly totals of observed cases in each of the next four weeks will be between 1,100 and 1,100 cases each week (Figure 2). However for the week ending April 03, the ensemble shows substantial uncertainty, with observed cases between 300 and 2,300 deemed possible (95% prediction interval: 343 - 2,282).

You can explore the full set of models, including their forecasts for past weeks online at our interactive forecast visualization.

Figure 2: Weekly observed and forecasted COVID-19 cases. Observed data from JHU CSSE and forecasts from the COVID-19 Forecast Hub.

Figure 2: Weekly observed and forecasted COVID-19 cases. Observed data from [JHU CSSE](https://github.com/CSSEGISandData/COVID-19/tree/master/csse_covid_19_data/) and forecasts from the [COVID-19 Forecast Hub](https://covid19forecasthub.org/).

For state-level case forecasts made over the last 6 weeks in Maine for which observed data are now available, the 95% prediction intervals covered the truth 88% of the time, and the 50% prediction intervals covered the truth 33% of the time. The forecasts on average over the last 6 weeks predicted values that were lower than the observed data.

The sortable and searchable table below shows the total number of reported COVID-19 cases at the US and state level for Maine as of Saturday, March 06, 2021 (“Total COVID-19 Cases”), as well as the weekly case count and rate of reported COVID-19 cases in the population (standardized per 100,000 population) over the last week (February 28, 2021 to March 06, 2021) and two weeks ahead (March 14, 2021 to March 20, 2021).

When interpreting probability of an increase, it’s important to note that the increase or decrease is relative to the location-specific recent observed incidence, which varies across locations.

County level

County-level case forecasts are presented in Table 3. Cases reported in unknown counties or by people who reside outside of the state are not included in Table 3, but are included in the state-level data.

This report was reproducibly and dynamically generated using RMarkdown. The code for the report can be found here.